Description -- Apache Ignite is a high-performance, scalable in-memory platform. It provides a wide variety of features such as advanced clustering, data grid through the standard JCache interface, streaming and CEP, compute and service grid, distributed messaging and events, Hadoop Accelerator, and Spark shared RDDs. It also implements memcached binary protocol, which enables existing applications to access data with various memcached client libraries. On the other hand, PostgreSQL extension called pgmemcache provides user-defined functions to access memcached in the database server process. This can be used to make database triggers refresh data cached in memcached.

Description -- Ehcache is the most widely used in-memory cache for Java objects. It can integrate with popular libraries and frameworks. For example, it can transparently cache data retrieved from PostgreSQL as a second-level cache for Hibernate ORM.

Description -- Infinispan is a distributed in-memory key/value data store with optional schema. One usage is a second-level in-memory cache for Hibernate ORM. Another usage is a key/value persistent store. The latter usage supports PostgreSQL as one of various storage backends -- Infinispan reads and writes data in PostgreSQL through JDBC.

Description -- Memcached is a distributed memory object caching system intended for speeding up web applications by alleviating database load. PostgreSQL extension called pgmemcache provides user-defined functions to access memcached in the database server process. This can be used to make database triggers refresh data cached in memcached.

Description -- BigMemory Max is a distributed in-memory cache that supports clients written in Java, C#, and C++. It can scale up to hundreds of terabytes of data in RAM distributed across multiple servers. BigMemory Max provides the most widely used Ehcache interface. Just like Ehcache, it can integrate with popular libraries and frameworks. For example, it can transparently cache data retrieved from PostgreSQL as a second-level cache for Hibernate ORM.